MBE

Photoluminescenceintensityenhancementhasbeenobservedforself-assembledInAsquantumdots
(QDs) coatedwithgoldnanoparticlesandassociatedtosurfaceplasmon(SP)couplingeffects.Thiseffect
wasinvestigatedfordifferenttemperatures,excitationenergy,laserpower,GaAscaplayerthickness,and
QD morphology.ItwasfoundthattheSP–QD couplingefficiency increaseswiththeincreaseofthe
temperature.ItwasalsoobservedthatthiseffectisenhancedforQDsgrownon(311)BGaAsoriented
substrates.

The effects of long time thermal annealing at 200 C on the optical
and structural properties of GaAs1xBix alloys were investigated by
X-ray diffraction (XRD), field emission scanning electron microscopy
(FESEM), high resolution transmission electron microscopy
(HRTEM) and photoluminescence (PL). FESEM images show that
bismuth islands nucleate on the surface and their diameter
increases after annealing. It was observed a PL intensity enhancement
and a small blue shift in PL peak energy after thermal annealing
at 200 C for 3 h of GaAs1xBix alloys which was associated to
the reduction of the density of defects. However these defects are
not completed removed by thermal annealing although an important
PL intensity improvement is observed.

Undoped GaSb is p-type with the residual acceptor concentration of about 1e17 cm-3 due to the gallium vacancies and gallium in antimony site. Counter-doping of GaSb with low level of Te can reduce the net carrier concentration resulting in higher optical transparency in a broad IR spectral range. In this work, the carrier concentration, mobility and sheet resistance of n-type and p-type Te-doped GaSb substrates were measured using Hall method at 300K and 77K. The Hall carrier concentration data at 300K were correlated with the absorption coefficients of GaSb in the IR spectral range. An empirical relationship between these values was established. Based on this correlation, we discuss application of FTIR spectroscopy for non-destructive optical screening of the substrates that allows construction of the carrier concentration distribution map across GaSb wafers. Investigations of the electronic properties of the low-doped p-type and n-type GaSb substrates upon cooling down to 77K indicate the reduction of the hole carrier concentration background for both GaSb types. This is evident from the decrease in the Hall-measured carrier concentration for p-type GaSb. For n-type GaSb, an increase in the carrier concentration is observed due to the reduction of the hole carrier concentration background.

This study aimed to evaluate the temporal change and accuracy of interpolation techniques used for spatial zonation of two groundwater quantity parameters including water table and depth to water table over 11 years. The study was conducted based on the data collected from piezometric wells of Sari-Neka Plain in Mazandaran Province, Iran. The investigated methods included a set of geostatistical approaches involving simple Kriging, ordinary Kriging, Radial Basis Function (RBF), and a deterministic interpolation method called Inverse Distance Weighting (IDW) with powers of 1 and 5. Subsequent to quality control and data normalization, the most appropriate variogram was chosen based on low RSS and high r 2 while the most suitable interpolation technique was determined regarding the cross validation, Mean Absolute Error (MAE), and Mean Bias Error (MBE). The results demonstrated that Simple Kriging was the most suitable method for zoning the depth to groundwater over the years 2001, 2006, and 2012. Meanwhile, the most suitable methods for zoning the water table included IDW with a power of 1for the year 2001, RBF for the year 2006, and IDW with a power of 5 for the year 2012. The important finding was that the interpolation methods showed a lower error for estimating water table than estimating depth to groundwater. This study also revealed a drop in water table in the study area over the 11 years' period. Meanwhile, new water table classes have been added and extended between the years 2006 and 2012 that had not existed five years earlier. The highest water table losses were observed in three points at 13m depth to water table in the middle and northern parts of the study area.

ABSTRAK ANALISIS PENGARUH TEGANGAN EKSTRAKSI TERHADAP DIAMETER SPOT BERKAS ELEKTRON MBE DI PSTA-BATAN DENGAN SIMULASI MENGGUNAKAN SOFTWARE SIMION 8.1. Mesin Berkas Elektron (MBE), telah banyak dikembangkan sebagai sumber radiasi pada proses iradiasi suatu produk industri. Di PSTA-BATAN telah dilakukan rancangbangun MBE dan untuk mencapai sesuai spesifikasi dilakukan pengembangan diantaranya dengan menambah tabung akselerator yang digunakan. Penambahan tabung akselerator akan mempengaruhi lintasan berkas elektron yang terjadi dan diameter spot berkas elektron pada window. Dengan demikian, diperlukan simulasi dengan tujuan untuk memprediksi lintasan berkas elektron yang terjadi dan ukuran diameter spot berkas elektron pada window. Simulasi dilakukan menggunakan software SIMION 8.1 dan didasarkan dari data-data geometri sumber elektron dengan elektroda Pierce, variasi tegangan ekstraksi dan tabung akselerator yang digunakan. Hasil smulasi menunjukkan bahwa makin besar tegangan ekstraksi maka makin besar energi berkas elektron keluar dari sumber elektron sehingga mempunyai kekakuan (rigidity) yang lebih tinggi dan tidah mudah dibelokkan. Akibatnya makin tinggi tegangan ekstraksi maka diameter spot berkas elektron sampai di window makin kecil. Diameter spot berkas elektron optimum diperoleh pada tegangan ekstraksi 10 kV dan 12 kV yaitu masing-masing d 1 = 5,41 ± 0,05 cm dan d 2 = 5,44 ± 0,05 cm. Kata kunci : lintasan dan spot berkas elektron, SIMION 8.1. ABSTRACT ANALISYS OF EXTRACTION VOLTAGE EFFECT ON ELECTRON BEAM SPOT DIAMETER OF EBM IN PSTA-BATAN WITH SIMULATION USING SOFTWARE SIMION 8.1. Electron Beam Machine (EBM), has been widely developed as a source of radiation in the irradiation process of an industrial product. In PSTA-BATAN has been designed and constructed of EBM and to achieve the required specifications an addition of accelerating tube has been added. The addition of an accelerating tube will influences the electron beam trajectory and the electron beam spot of diameter at the window. Therefore, a simulation required with the aim to predict the electron beam trajectory and the diameter of the beam spot.. Simulation was done using SIMION 8.1 software and based on geometry data of electron gun with Pierce electrode, an extraction voltage and accelerator tube were varied. The results show that the greater of extraction voltage, the greater the electron beam energy so that it has a higher rigidity and thisis not easily deflected. As a result, the higher the extraction voltage, the diameter of electron beam spot reaches the window is smaller. The optimum diameter of beam spot was achieved at the 10 kV and 12 kV of extraction voltages. At this condition the diameter is d 1 = 5.41 ± 0.05 cm and d 2 = 5.44 ± 0.05 cm respectively.